POSITIVE TRAIN CONTROL

This article summarizes the major aspects of positive train control systems, which use satellite global positioning technology, electronics and on-board computers to regulate trains' speeds and help them avoid collisions. Evidence is still needed to show that the systems can raise productivity enough through shorter headways, higher velocities and increased track capacity to offset their cost. Seamless interoperability is also an issue. Despite these problems, some kind of positive train control system is expected within the next 10 years.